Device having a glow-discharge indicator tube for reproducing signs and glow-discharge tube for use in such a device



N v. 1 1969 H.J.G. M. VAN DAELEN DEVICE HAVING A GLOW-DISCHARGE INDICATOR TUBE FOR REPRODUCING SIGNS AND GLOW-DISCHARGE TUBE FOR USE IN SUCH A DEVICE Filed Nov. 17, 1967 2 Sheets-Sheet 1 INVENTOR. HENRI J GM VAN DAELEN FEEL? AGENT Nov. 18. 1969 H J. G. M. VAN ELEN 3,479,547

DISCHARG DEVICE HAVING A GLOVi- E INDI TOR TUBE FOR REPRODUCING SIGNS AND GLOW-DISCHARGE TUBE FOR USE IN SUCH A DEVICE Filed Nov. 17, 1967 2 Sheets-Sheet 2 G 2 VENTOR.

HENRI J .G.M .VA AELEN BY M 8 AGENT United States Patent U.S. Cl. 313-1095 Claims ABSTRACT OF THE DISCLOSURE A glow discharge tube for displaying various indicia comprises a cathode, an anode, and a plurality of conductive segments positioned adjacent the display window. A body of opaque insulation material having holes therein is interposed between the anode and the segments and is arranged to form a plurality of ducts ending on the segments. The segments are selectively energized to produce a plurality of luminous column discharges in accordance with the indicia to be viewed.

The present invention relates to display and devices more particularly to a display having a glow-discharge tube for reproducing symbols consisting of luminous segments. The invention further relates to a glow-discharge tube for use in such a device.

When symbols for example, digits, letters, punctuation marks, signs for electric quantities and the like, are composed of a number of segments, the advantage is obtained that a large number of symbols all lying in one fiat plane can be composed of a comparatively small number of segments.

In the known display tubes, the segments consist of glow-discharge cathodes which are arranged freely or are embedded in insulating material. In both cases, there arises the disadvantage of cathode sputtering and the inherent blackening of the bulb window. This blackening cannot be completely eliminated by arranging a grating in front of the window, especially because in the case of symbols composed of segments, with regard to the reproduction, the grating used cannot be so fine-meshed as in the case of consecutively arranged complete symbols.

Owing to the sputtering, the glow-discharge current to the segments, and hence also the brightness, are limited with regard to the life that can beattained.

A construction is also known which consists of a stack of square insulating plates provided with a quadratic pattern of holes. These plates have sandwiched between them a number of anode plates each having the form of a symbol and provided with holes corresponding to the holes in the insulating plates. The stack is clamped between a conducting non-perforated plate and a conducting perforated plate covered with a transparent or a translucent plate. In accordance with the anode plate switched on, a cathode glow-light appears in a number of holes of the pattern of the symbol chosen, as a result of which a more or less bright reproduction of the symbol is obtained. If the non-perforated covering plate is connected as the cathode, this results in a strong vignetting, whereas if the perforated plate is connected as the cathode, a disturbing blackening of the covering plate soon occurs owing to cathode sputtering. Sputtering also causes a short circuit between the various cathode plates adjoining a duct formed by the holes.

3,479,547 Patented Nov. 18, 1969 The invention has for an object to provide a tube and a display device which have advantages when compared with the known tubes and devices More particularly, an object of the invention is to provide a display tube that is compact in size, requires relatively low operating voltages, exhibits a relatively high efliciency, and is not subject to cathode sputtering problems.

In a device utilizing a glow-discharge tube for reproducing symbols, composed of luminous segments, according to the invention, a voltage is applied between the anode of a glow-discharge tube and the relevant segments such that a discharge current flows to these segments. The discharge path to the segments is narrowed by providing insulating material arranged to form one or more parallel ducts ending on the segments so that a luminous column discharge is produced therein.

In the arrangement according to the invention, the

light of the cathode-anode glow discharge is preferably screened by the anode as far as possible, so that also the advantage is obtained that its sputtering products cannot influence the visibility of the light produced by the column discharge. Due to the fact that the light of the column discharge is used instead of that of a cathode, the brightness may be considerably greater while sputtering need not be feared. The production of light in the column is also more satisfactory than in the cathode glow, so that the development of heat is small. As a result, the efficiency of a positive column of light at the segments is relatively high. The required control voltage between the anode and segments is then low, i.e. relatively approximately 30 or 40 volts.

A particularly advantageous embodiment of a glowdischarge tube according to the invention is characterized in that the segments consist of frame-shaped metal layers mounted on a glass plate over which is disposed an opaque plate of insulating material which is provided with perforations aligned with the segments.

A very compact arrangement according to the invention is obtained if this glass plate at the same time constitutes the window of the bulb. In this case the glass plate and the remaining cup-shaped part of the bulbs are secured to each other with the aid of enamel or a similar material. Thin metal layers integral with the segments then fulfil the function of supply conductors. The cup-shaped bulb part need accommodate only the lead-in wires of the anode and the cathode.

Because a glow light uniformly spreading over cathode parts is not used, the tube is considerably less sensitive to the purity of the gas filling. Consequently, the tube life may also be very long, and the addition of mercury to the gas filling is not necessary. In order to limit the development of heat in the primary glow discharge, use may be made of an activated cathode. In view of the low control voltage, the overall voltage across the tube is then low. Furthermore, the system eliminates the problem of blackening of the display window due to cathode sputtering.

With a sufficiently fine subdivision into a number of segments, both digits and letters can be reproduced on the same surface with sufficient brightness.

The segments and the lead-in wires disposed on the same glass plate in accordance with the invention provide the possibility of arranging on one glass plate a number of adjacent symbols each having an individual primary glow discharge, while only one bulb is used.

The invention will now be described more fully with reference to the drawing, in which FIGURE 1 is a sectional view of a glow discharge tube according to the invention taken parallel to the axis and at right angles to the window, FIGURE 2 shows a few parts thereof in a disasembled state, and FIGURE 3 shows diagrammatically a circuit arrangement. Referring now to FIGURE 1,

reference numeral 1 denotes a glass plate on which are deposited a number of segments 2 of gold having a thickness of 10,11. and lead-in wires 3 connected thereto. On these segments bears a mica plate 4 having a thickness of 0.8 mm. and provided with round holes 5 having a diameter of 0.8 mm. The segments 2 consist of circles having an inner diameter of 0.5 mm. and a width of 0.3 mm. and a plurality of straight segments each consisting of two strips spaced apart by a distance of 0.5 mm. and interconnected by two transverse strips. The holes 5 in the mica plate are arranged so that one hole is located at each circular segment 2, whereas three to four holes are located at each straight segment. The mica plate 4 is rendered opaque by spraying it with a layer of chromium oxide 12 having a thickness of 50 microns. The anode of the glow discharge tube is constituted by an iron plate 6 coated with aluminum, whereas the cathode is constituted by a nickel plate 7 coated with an emitter composition such as barium oxide. The bulb 8 is secured to the glass plate 1 with the aid of enamel edges 9, as a result of which the mica plate 4 is also fixed. The gas filling consists of neon containing 0.1% of argon at a pressure of 250 Torr. At an operating voltage of approximately 50 v., a current of approximately 10 ma. passes between the cathode 7 and the anode 6, whilst the maximum current to the segments is approximately 5 ma; at a voltage difference between anode and segments of approximately 30 v.

In FIGURE 3, a voltage source 10 of 50 v. with a series resistor for limiting the current to the desired value is connected between the cathode 7 and the anode 6. A second voltage source 11 of 40 v. is connected through series resistors and switches to the segments 2. An advantage of the three electrode system disclosed is that only a relatively low voltage is needed between segments and anode to produce a good display. Since the anodecathode voltage is relatively low, the total voltage across the tube is low.

What is claimed is:

1; A display device comprising, a gas-filled glow discharge tube having a transparent window, a plurality of conductive segments positioned adjacent the inside surface of said window, a cathode mounted in said tube, an anode mounted between said cathode and said segments in spaced apart relationship therewith, insulation means positioned in the discharge path between said anode and said segments and arranged to form a plurality of parallel ducts ending on the segments, means for applying a voltage between said anode and cathode, and means for selectively applying a voltage between said anode and given ones of said segments so that a discharge current flows to the selected segments thereby to produce a luminous column discharge between each of said given segments and the anode.

2. A device as claimed in claim 1 wherein said anode comprises an opaque plate-like member arranged to screen the light produced by the anode-cathode glow discharge.

3. A device as claimed in claim 2 wherein said segments comprise frame-shaped metal layers and further comprising a glass plate on which said segments are mounted, said insulation means comprising an opaque plate of insulating material covering said glass plate and segments and including a plurality of holes in registration with the segments.

4. A device as claimed in claim 3 wherein the glass plate on which the segments are disposed also constitutes the window of the tube, means for securing the glass plate and the remaining part of the tube to each other by means of enamel or a similar material, and supply conductors for the segments comprising a plurality of thin metal layers integral with the segments on the glass plate.

5. A device as claimed in claim 1 further comprising a glass plate within said tube on which said segments are mounted, said segments being divided into two or more segment groups corresponding to two or more individual symbols to be displayed.

6. A device as claimed in claim 1 wherein said anode is maintained at a positive voltage with respect to the cathode sufiicient to establish a glow discharge therebetween and said given ones of the segments receive a positive voltage with respect to the anode voltage.

7. A display device comprising, a gas-filled glow discharge tube having a transparent window, a plurality of conductive segments positioned adjacent the inside surface of said window, a cathode mounted in said tube, an anode mounted between said cathode and said segments in spaced apart relationship therewith, an opaque plate composed of insulating material positioned between said anode and segments and containing holes aligned with the segments to provide a plurality of discharge paths between the anode and the segments, a first source of voltage directly connected between said anode and cathode for establishing a glow discharge therebetween, a second source of voltage, and switching means for selectively interconnecting said second voltage source between, said anode and selected ones of said segments to establish a luminous column discharge between each selected segment and the anode in accordance with the symbol to be displayed.

8. A device as claimed in claim 7 wherein all of said segments are mounted in a single plane that is approximately parallel to the surface of the window and to said opaque plate.

9. A display tube comprising, a gas-filled glow discharge tube having a glass window, a plurality of conductive segments mounted on the inside surface of said window, an anode spaced apart from said segments, an opaque plate of insulating material mounted adjacent said window between said anode and segments, said plate having a plurality of holes in registration with said segments, a cathode spaced apart from said anode, means for applying an ionizing potential between said anode and cathode, and means for selectively energizing given ones of said segments to produce a plurality of luminous column discharges between said given segments and said anode in accordance with the indicia to be viewed.

10. A tube as described in claim 9 wherein said segments comprise a first plurality of rectilinear metal members and a second plurality of curvilinear metal members arranged in the same plane.

References Cited UNITED STATES PATENTS 2,558,019 6/1951 Toulon.

2,848,638 8/1958 Smith 313--109.5 2,595,617 5/1952 Toulon.

3,133,221 5/1964 Knochel et al.

3,260,880 7/1966 -Kupsky 3l3109.5

JAMES W. LAWRENCE, Primary Examiner D. OREILLY, Assistant Examiner U.S. Cl. X.R.

11313; UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION pa e N 3479547 Dated November 18, 1969 Inventor) HENRI J.G.M.VAN DAELEN It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

col. 1, line 29, cancel "and devices" and insert devices and col. 1, line 30, after "display" insert device col. 1, line 34, after "symbols" insert a comma col. 2, line 30, cancel "low, i.e. relatively" and insert relatively low, i.e.

Signed and sealed this day 26th of Mav 19 70 (SEAL) .Attest:

EdwardM. Fletcher, It. WILLIAM E. Sam m Co Attesting Officer missimer atents 

